A similar type of valve adjusting device is known in principal from DE-OS 30 24 109 corresponding to U.S. Pat. No. 4,455,543 (Pischinger et al).
This known device discloses a gas exchange valve for an internal combustion engine wherein the valve stem is joined to a valve disk and includes a control element which is alternatingly moved by assistance of a spring system to two discrete operating positions and is retained thereat by either switching magnet, causing the valve to open or close. It is desirable to have improved fast switching time behavior in this type of system to optimize valve timing. Fast switching time behavior is defined as the shortness in time it takes the compression force of a spring to overcome a decaying electromagnetic force of a de-energized switching magnet in order to accelerate the control element to the other operating position.
Pischinger teaches to increase the operating frequency of the actuator assembly by reducing the masses to be accelerated. This is accomplished by connecting a uniformly thick armature to the control element (in this case a poppet valve) such that the armature is positioned between the two opposed switching magnets. Since the armature undergoes numerous cycles of pole surface impact over the operating life of the actuator assembly, the armature of this system must be sufficiently thick to withstand material fatigue and failure, thus the amount of mass that can be reduced to achieve improved time switching behavior is limited.
Other examples of solenoid actuated switching devices for gas exchange valves rely solely on electromagnetic means for providing the forces of motion for the valves.
GB 568 216 discloses an electromagnetically based positioning device for gas exchange valves, in which two opposed, push-pull type annular solenoid coils move a laminated iron field spool back and forth therebetween under alternating excitation. This motion is transmitted via a plunger to the valve disk of a gas exchange valve to open and close the valve. Each coil has provided along its inner annular surface an iron core which is tapered such that the inner annular surface forms a receiving socket for engagement with a correspondingly tapered side of the reciprocating field spool. The coils lie against the lateral wall of a truncated cone, and the field spool is designed in such a way that it cannot be drawn freely into the coils, but instead the beveled faces of the field spool and the core form a stop piece. In order to transmit sufficient force, each core is heavy and massive, so that short switching times between the open and closed position cannot be achieved with a system of this kind.
BE-A 889 856 discloses a similar design, in which an armature having opposed conically shaped end faces is also moved into two axially arranged, alternately excited coils, interacting with a corresponding conical pole stopping face associated with each core. Once again, the core of each coil is heavy and clumsy, which prevents fast switching times of the system.
EP-A 38 128 is an example of a similar design for a solenoid actuated pilot spool valve using large mass elements but is directed toward use in hydraulic systems.
All of the above examples share the disadvantages of less than optimal fast switching time behavior due to the high mass designs of their moving elements i.e, armature, field spool, etc. Thus, there is a definite need in the art for solenoid actuated adjusting device for gas exchange valves in internal combustion engines which use moving elements of low mass design while ensuring the physical integrity of the moving elements and reliability and accuracy of the switching behavior over long operating lifetimes.